Fresh from a study visit to the Center for Evolutionary Psychology at the University of California, Santa Barbara, Clasen believes the timeless, cross-cultural appeal of horror fiction says something important about humans, and in turn, insights from evolutionary psychology can make sense of why horror takes the form it does. 'You can use horror fiction and its lack of historical and cultural variance as an indication that there is such a thing as human nature, ' he says. This nature of ours is one that has been shaped over millennia to be afraid, but not just of anything. Possibly our ancestors' greatest fear was that they might become a feast for a carnivorous predator. As science writer David Quammen has put it, 'among the earliest forms of human self-awareness was the awareness of being meat'. There's certainly fossil evidence to back this up, suggesting that early hominids were preyed on by carnivores and that they scavenged from the kill sites of large felines, and vice versa. Modern-day hunter-gatherers, such as the Aché foragers in Paraguay, still suffer high mortality rates from snakes and feline attacks. Such threats have left their marks on our cognitive development. Research by Nobuo Masataka and others shows that children as young as three are especially fast at spotting snakes, as opposed to flowers, on a computer screen, and all the more so when those snakes are poised to strike. Modern-day threats, such as cars and guns, do not grab the attention in this way. That we're innately fearful of atavistic threats is known as 'prepared learning'. Another study published just this year by Christof Koch and his team has shown how the right amygdala, a brain region involved in fear learning, responds more vigorously to the sight of animals than to other pictures such as of people, landmarks or objects. Viewing the content of horror fiction through the prism of evolutionary evidence and theory, it's no surprise that the overriding theme of many tales is that the characters are at risk of being eaten. 'Do we have many snakes or snake-like creatures or giant serpents in horror fiction?' Clasen asks. 'Yes we do: look at Tremors - they were really just very big snakes with giant fangs'. In fact, many horror books and movie classics feature oversized carnivorous predators, including James Herbert's The Rats, Shaun Hutson's Slugs, Cat People, King Kong, and the Jaws franchise, to name but a few. Where the main threat is a humanoid predator, he or she will often be armed with over-sized claws (Freddie Krueger in Nightmare on Elm Street) or an insatiable taste for human flesh (e.g. Hannibal Lecter in the 1981 novel Red Dragon).